We did this trip last fall, and opted to bypass the Atlanta/Chattanooga route. We took I-64 from St. Louis and got onto I-57 at Mt. Vernon, IL. At Marion, IL, we got on I-24 and took it all the way to Nashville, TN. We hit I-65 at Nashville down to Montgomery, AL. From Montgomery we took US highway 231 down to I-10 in the Florida panhandle. Then across I-10 to connect with I-75 at Lake City, and down south to central Florida. Highway 231 is a 4 lane divided highway, but is not controlled access like interstates. It was a nice ride all the way down.